in a pickle, I'll try to explain best I can.

So I shoot off camera flash whilst out in the field, this is the setup. canon 600ex-rt II flash with a St-e3-rt transmitter on camera, had it this way for years, set to HSS and all was working well..........
now for some reason ( and no setting have been changed ) when I " lockdown " the St-e3-rt to the hotshoe , the camera jumps to 1/250 max speed??? if however I don't lock it down then HSS is achieved??? iv also noticed that if I change flash power on the transmitter it does not change power settings on the flash?? I have to fire the "test" button on the transmitter to change the power on the flash?? iv tried different cameras to see if it was a hotshoe issue and still the same issue...
hope this makes sense and someone may have a solution..... cheers all